Jump to content
Sign in to follow this  
tneker

Carbon build up on piston and exhaust ports

Recommended Posts

Now that I have already cleaned up some carbon build up on pistons and in exhaust ports from what was less than about 24 race hours I can't take any pictures to make my question more meaningful.  Long story short, I was surprised by the amount of carbon build up after less then 24 hours of racing on a fresh build.  We run about 12.8 AFR at WOT and idle may be around 13.5 on a port injection dual overhead cam 4 cylinder.  

 

What are your experiences, is that typical given the conservative AFR?  Is WOT or idle a bigger contributor to build up?  

 

 

Share this post


Link to post
Share on other sites

12.5:1 was typical of what a carbed engine needed to keep the leanest cylinder from burning up. 13.2-3 is now considered the norm for EFI stuff.

 

Port fuel injection has essentially even fuel distribution (barring a bad injector) and can achieve the same goal with an AFR that is 0.5 to 1.0 points higher. Add in better ignition systems and combustion chamber design and you can bump that another 0.5 but that's starting to run it on the edge.

 

I ran my V6 pushrod (wedge combustion chamber) engine at 13.5-13.8 at WOT and had very little carbon build-up after 80 hours. WOT uses the most fuel and will deposit the most hard carbon if running too rich.

  • Like 1

Share this post


Link to post
Share on other sites

Do you still have an EGR valve on your engine? That is usually the biggest contributor to carbon buildup that I see. Also, 24 hours of racing is probably more WOT time than a few years of driving around town.

Share this post


Link to post
Share on other sites

Your afr is solid. I would never run something less than 12.8..or higher if you will, especially FI.

 

I agree,  pcv is a killer.

 

 what engine, etc?

Share this post


Link to post
Share on other sites
21 hours ago, UngluckInc said:

Your afr is solid. I would never run something less than 12.8..or higher if you will, especially FI.

 

I agree,  pcv is a killer.

 

 what engine, etc?

2.4 DOHC out of a PT Cruiser.  No EGR, and crankcase vent is one line to a catch can.  Will look at also using the other valve cover port that is currently just plugged.

Share this post


Link to post
Share on other sites
On 3/2/2019 at 1:47 PM, Scribe said:

Do you still have an EGR valve on your engine? That is usually the biggest contributor to carbon buildup that I see. Also, 24 hours of racing is probably more WOT time than a few years of driving around town.

No EGR on this particular version of the Chrysler 2.4 engine.  Typically don't tear down after only 24 hours, so maybe just a perception thing.

 

Share this post


Link to post
Share on other sites
On 3/7/2019 at 8:18 PM, tneker said:

2.4 DOHC out of a PT Cruiser.  No EGR, and crankcase vent is one line to a catch can.  Will look at also using the other valve cover port that is currently just plugged.

 

Bad idea. 

 

Only one of those is well baffled, you will find out the first time you race witg sustained high g right handers at high rpm\wot....the oil loss\rustproofing is impressive. ..

  • Like 1

Share this post


Link to post
Share on other sites
58 minutes ago, Black Magic said:

 

Bad idea. 

 

Only one of those is well baffled, you will find out the first time you race witg sustained high g right handers at high rpm\wot....the oil loss\rustproofing is impressive. ..

 

Not yet. There are three different types of valve covers for late 2.4 heads. Aluminum, composite and a quasi turbo valve cover that doesn’t say turbo.

 

so unless we know which one, it’s a guess. But you are correct some are baffled well and others not so much.

  • Like 1

Share this post


Link to post
Share on other sites
15 hours ago, Mopar 4 Life said:

 

Not yet. There are three different types of valve covers for late 2.4 heads. Aluminum, composite and a quasi turbo valve cover that doesn’t say turbo.

 

so unless we know which one, it’s a guess. But you are correct some are baffled well and others not so much.

 

He runs pt engine (sbec gen) so it has to be the composite, which you want to vent the pcv port and not the air makeup. 

Edited by Black Magic

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...